Silicon Systems Moving Some Workers Out of Orange County: The Tustin-based company, which makes computer circuits, confirmed that it is moving its manufacturing operations. The privately held company, a subsidiary of Tokyo-based TDK Corp., said it will keep its corporate headquarters, main design center and about 800 of its employees in Tustin. It will move its remaining 150 manufacturing workers to a new plant, to be built at a site not yet chosen. Silicon Systems employs about 2,000 people worldwide, mostly in Tustin, Santa Cruz and Singapore. The company said it is considering locations in Oregon, Nevada and the Sacramento area.